1. Field of the Invention
This invention relates generally to light projection apparatus, and in particular to a spotlight or floodlight of the type suitable for stage lighting.
2. Description of the Prior Art
Conventional illumination systems, especially for soft lighting or spot flooding applications, are somewhat inefficient and complex. For stage lighting and studio lighting applications, the spot projectors must be adapted to vary the area of illumination to accomodate different stage settings. The inefficiency of conventional projectors used for this purpose usually requires the use of two or more projectors to produce the desired illumination. Additionally, projectors that have the capability of producing a variable area of illumination are generally expensive in terms of the large number of lenses which must be kept on hand so that specific combinations of lenses can be selected for producing a particular illumination effect.
Equipment for stage lighting and the like has undergone significant changes over the last 50 years. Early designs for plano-convex spotlights included a lamp, a plano-convex lens and a reflector. These conventional units have been replaced by fresnel lenses and ellipsoidal reflector spotlights. The advances in these units have been primarily in mounting construction, rather than optics and efficiency.
In the early development of elipsoidal spotlights, only two sizes were in common use: a 250-500-750 watt unit with two 6 inch diameter by 9 inch focal length lenses mounted together and movable as a single lens for focusing, and an 8 inch diameter by 12 inch focal length lens unit using 1000-1500-2000 watt lamps. The use of the 8 inch diameter units has for the most part been discontinued. The most commonly used ellipsoidal units to date include 31/2 inch, 41/2 inch, 6 inch, 10 inch, 12 inch and 14 inch lens diameter units with a power rating of 300-1000 watts.
The number of lens combinations for practical spotlights is around 50. The cost of these units in recent years has increased as much as five times. The use of these numerous lens variations has become so costly and complicated that an experienced designer is required to specify a lens combination for a particular stage application.